HOUSTON — Hours before President Trump was set to arrive in town to campaign for Republican Ted Cruz in Texas’s closely watched Senate race, Democrat Beto O’Rourke was bounding through the parking lot of a shopping center here, mobbed by hundreds of supporters as he made a predawn visit to a polling place on the first day of early voting in the state.

It was the first of eight scheduled “pop-up rallies,” as O’Rourke referred to them, in and around Houston on Monday in what will be an all-out ground war until Election Day as the El Paso congressman vies to become the first Democrat elected to statewide office since 1994.

“It’s finally here!” O’Rourke exclaimed, as he made his way through a mob of people pushing their way toward the congressman, whose celebrity candidacy has attracted enormous crowds and intense media attention. “This is the largest grassroots campaign in this state, perhaps this country, and it is starting right here.”

Texas Democratic Senate hopeful Beto O’Rourke campaigns near a polling site as early voting kicked off Monday in Houston. (Photo: Holly Bailey/Yahoo News)

O’Rourke’s first stop was about 10 miles from downtown Houston, where Trump and Cruz will appear together on Monday night. But in an interview, the Democratic hopeful insisted his schedule in Houston was not an attempt at counterprogramming. Campaign officials said he had planned to be here long before the president’s visit was announced. “Just a happy coincidence,” O’Rourke said with a sly smile.

Standing on a chair and speaking through a bullhorn, O’Rourke delivered an abbreviated version of his usual stump speech, appealing to Texans from both parties to rise above partisanship and division and to vote for a candidate focused on “big, ambitious goals” that defy party orthodoxy — like him.

“Everything we care about … is on the line,” O’Rourke declared. “We’ll be defined by the people of 2018. This is our moment. This is our chance. This is our message for the people of the future while we can still get it right.”

What O’Rourke did not talk about Monday or in rallies over the weekend was Cruz or Trump — an omission that was notable after several days in which the congressman went on the attack against his GOP opponent, a tactic that conflicted with his pledge to run a positive campaign.

A woman holds up a portrait of Barack Obama at an O’Rourke rally in Houston. (Photo: Holly Bailey/Yahoo News)

While O’Rourke insisted his new approach was an attempt to offer a stronger “contrast” between his record and Cruz’s — “and I don’t think there’s anything negative about [that]” — he said he believed most voters wanted him to stick with the hopeful message he’s championed on the trail for the last year and a half.

“They don’t want to hear me talk about another party, another person,” he said. “They want to hear me talk about the future, their future, their kids’ future, and that’s what we’re going to stay focused on.”

Before heading to the next stop, O’Rourke led his army of supporters across the street to the polling station, where dozens of people had been lined up for hours to vote — including a group of college kids who had pitched a tent the night before so they could be first in line to cast their ballots.

At one point, the lanky 6’4” congressman dove into the small blue tent, which was decorated with “Beto for Texas” stickers and signs. “It’s the support from people like you that keep me going,” he told them, as a mob of media and supporters trying to catch a glimpse of the candidate inside nearly collapsed the tent.

Supporters of O’Rourke camp outside a polling site ahead of early voting. (Photo: Holly Bailey/Yahoo News)

“Everybody has to go vote,” O’Rourke told his supporters. “When we reach out to our classmates, our colleagues, our neighbors and our family members, remind them that this is the election of our lifetime.”

But first, O’Rourke said, he urged those around him to look up at the sky, which through the wispy clouds was a perfect shade of azure blue as the sun began to rise. It had been raining for days here, and the forecast said it would begin raining again later Monday, in a washout that would last through the week. But right now, O’Rourke said, staring up, it was “perfect.”